The purpose of this study is that an adductor canal nerve block (putting numbing medicine near the nerve) has been shown to produce excellent pain relief with less pain medication use after knee replacement surgery.The investigators will be comparing the amount of pain relief following knee replacement surgery when you have a nerve block in place. There will be approximately 66 subjects participating in this study. After surgery subjects will receive numbing medication every 6 hours for 48 hours. Subjects will also receive a morphine PCA (patient controlled analgesia) after surgery and pain medication by mouth every 4 hours around the clock with the option to receive more pain medication if needed. Subjects will participate in the study up to 3 days.